HP LP3065 Power Supply Details

[Electronomo]

Hi everyone - Just thought I would share a few details about the repair of my LP3065 power supply. The monitor would exhibit the 2 seconds to black issues detailed in other posts. I tested the CCFL lamps via an external supply and found all 9 sets to be working OK. I tried to replace the inverter board (salvaged from a Dell 3008) and still no-go. I then removed the power supply for testing independent of the monitor. I found that you have to load the output voltages to properly test the unit. I used resistive loads for about a 1 amp load on the 5VSB, 18 and 24 volt outputs. This supply uses an L6561 Power Factor Correction/boost regulator (8 pin SOIC in one corner of back side of PC card) just beyond the bridge rectifier to provide a V+ of about 400 Vdc when properly functioning. The 5VSB supply is developed via an SG5842 IC(only other 8 on SOIC on rear of board). The +18 and +24Vdc outputs are developed via the L6598 IC on the top side of the PC board (16 pin dip partially hidden by heatsink plate). I could read some of the part numbers on the ICs. The others I read under a microscope while bathed with isopropol alcohol. As the alcohol evaporates there is a short interval where the alcohol in the depressions of the part number remains so you can just make out the number for a few seconds. In the end the problem with the supply was an open resistor in a divider network that supplied a half wave signal to the L6561 from the bridge rectifier which made the L6561 unstable and the supply would cycle on and off. I put a lot of effort into reverse engineering the design and creating schematics as best I could but I don't trust them enough to publish them. I want to close with the typical cautionary statement - Please be careful if you're going to work on the HOT side of SMPS devices as the results of any mistakes can be fatal.

[budm]

Re: HP LP3065 Power Supply Details

That is why I recommend to use Isolation transformer (Neutral NOT tied to Ground on the outlet) for the UUT specially if you are going to use the scope on the Primary side of the circuit, and at least plug the UUT into GFI outlets.

[jetadm123]

Re: HP LP3065 Power Supply Details

Thanks for sharing! I don't suppose you would remember which resistor id it was, Rxxx, or what value it was?

[Electronomo]

Re: HP LP3065 Power Supply Details

R102 - 620k